1. Military aspects on the use of Mode S and Mode S related Systems
Ladies and Gentleman,
I will give You a presentation on the military aspects on the use of Mode S as seen today by the German Armed Forces.
This is not a harmonised EUROCONTROL position but as ervery military force is confronted with the same aspects of civil ATC and ATM the facts we found out and the requirements we derived from are applicable to nearly every military force worlwide.
An other limitation in this presentation is the time factor. During the next 20 minutes I can only highlite some aspects but can not go to details.

2. Military Operational Requirements on Identification
Structure
Military Operational Requirements on Identification
Conflict areas identified due to the civil use of Mode S
Improvements of military systems using Mode S
Military Mode S Architecture
Military applications for Mode S based Systems
My presentation is roughly structured as follows:
I will speak on the mil ID requirements, but will also mention the
conflict areas in civil/military interoperability due to the Mode S implementation in the civil world.
By using Mode S we from the military community may improve the performance of mil Systems.
To do this we have to adopt some civil architectural ideas in mil systems,
and last but not least I will discuss some few of many possible mil applications of Mode S related mil Systems.

3. NATO Military Operational Requirement (MOR) on Identification
Aircraft IFF
Fighter Bomber
Fighter Aircraft
Air/Ship to
Ground ID
Ground ID System
Close Air Support
Mode S
Here You see the graphical interpretation of the military operational requirement on ID as it is laid down in the NATO MOR on ID.
You see the different ground-, seabased and airborne Systems and their ID requirements against each other.
But often the interoperability approach between civil and military systems is forgotten which could clearly be seen in the different definition on
Identification Friend and Foe or
Monopulse Secondary Surveillance System which includes much more than simply ID.
Anti-Tank
Helicopter
FO/FAC
Warship
Ground Vehicle
SAM
Long Range Surveillance

4. Civil Mode S Traffic Scenarios
3700
Mode S
Conspicuity Code
3700
3700
FL 100
3700
Mode 3/A
2711
3711
4711
One of the benefits of Mode S is that all A/C have one discrete 24 Bit adress and reply with their Flight Plan Callsign if interrogated properly. Therefore they don‘t need a discrete 3/A Code.
But this benefit for Mode S systems is a problem for older IFF/SSR systems. They can identify different platforms only by 3/A Codes.
Therefore different traffic scenarios were developed by DFS for Germany to allow a smooth transition between Mode S and non Mode S areas.
If started and landed in a Mode S area without interruption just a conspicuity code is used.
If started in non Mode S there is a discrete 3/A allocated until reaching the Mode S area.
If landed in a non Mode S area a 3/A Code is allocated before handover and if flying only in a non Mode S area a discrete 3/A Code is allocated during the whole flight.
GND
ASR
ASR
ASR
complete Mode S flightpath
Conspicuity Code
3/A Group Code
Mode 3A/ Mode S flightpath
3/A Group Code
Conspicuity Code
Mode 3A flightpath

5. IFF 3/A- versus Mode S Interrogation Capability
3700
LH 123
4711
3700
BA 5643
3700
GAF 2213
In an Mode S environment all A/C have the same Code. In this example Conspiquity Code 3700.
Without Mode S capability all interrogators, wether land-, sea- or airbased get all A/C with the same 3/A conspicuity Code. Only A/C with discrete Codes can be identified.
3A Code, common IFF
Flight Plan Callsign (ID)
With Mode S

6. Propability of acquisition for different Lock-out procedures
200
180
160
140
without lock-
out
120
100
with lockout 80 60
To interrogate with Mode S there are only 15 non zero Interrogator Identifier Codes and 63 Surveillance Identifier Codes available.
As this number is even not sufficient for the civil systems, there were discussions that military interrogators should not use non zero II-Codes but only II-Code zero in combination with lock out override procedures.
Studies clearly showed that due to the RF-Load there is a big difference for the No. of needed interrogations for acquisition propabilities > 99% with and without lock-out
and non lock out procedures. 40 20 2 3 4 5 6 7 8 9 10
No. of needed interrogations for acquisition propability > 99% with and without lock-out

7. Propability of acquisition for different Lock-out procedures
In this viewfile the number of necessary antenna revolutions are compared beeing necessary to acquire 100% of all targets within the coverage area of a Mode S radar with different statistical lock-out procedures.
is to reply with every interrogation
is to reply every second interrogation
is to reply every 4th interrogation and
0.125 is to reply every 8th interrogation
No. of acquired Transponders in % depending on the number of antenna-turns

8. Summary on acquisition Strategy
The use of lock-out procedures based on different Interrogator Codes is at least for all fixed military Mode S Sensors absolutely necessary !!!
For the acquisition of a/c flying in close formation a stochastic acquisition procedure depending on the number of a/c improves the performance of the mode S sensor very much !!!
Self explanatory

9. Beneficial use of Mode S on airborne Interrogator platforms
The Radar Antenna is large against the used wavelength
therefore its beam is relatively sharp.
For airborne platforms with Mode S capability there is an additional benefit in using Mode S.
Not only the Mode C Height even, the 3 dimensional position of the target could be extracted.
So additional ID parameters are available to enhance the ID process.
The IFF Frequency is much lower,
so the Beam of the IFF Antenna is quite broad.
One of the 4 targets with identical range has to be
Identified, but which is it?
With Mode S the position of all responding Targets could be extracted and the target identified

10. German military ATC and Long Range Air Defense Radars
If the GAF is using just one Interrogator-Code for their mil Radars with ATC related services, that means military ATC and Long Range Air Defense, this code is unusable for all other countries in the Mode S core area.
Because of the big number of radars the information exchange only to overcome the lock-out problem in between these radars is consuming more of the data communication capacity than to be needed to connect all the radars to the Control and Reporting Centers and the Airport Approach Control.
Therefore we have to groupe the mil Interrogators and use one Interrogator Code for each cluster of Interrogators.
Figures EUROCONTROL 10/99

11. EUROCONTROL ICAT Tool, II Code 5 (DFS Cluster South)
Due to the limited II-Code availability Mode S Interrogators have to be clustered. That means they use the same II-Code and inform each other on the targets under lock out condition.
This slide shows an example for a cluster in the southern part of Germany using the same II-Code.
An other radar at UK without overlapping the GE cluster uses the same code.
EUROCONTROL Interrogator Code allocation Tool

12. Civil and military Cluster sizes
6 civ.Radarstations with Cluster Code 3
II3
II3
II3
II3
Civil Cluster of 6 radars with overlapping coverage of 2 military Long Range radars.
II3
2 mil. Long Range Radarstations with overlapping Coverage
II3

13. Parallel use of identical II Codes in overlapping clusters
Folie 3
Parallel use of identical II Codes in overlapping clusters
II Code: 3
II Code: 3
Regional Civil
Control Center
Enroute Traffic
Track Server
When 2 Clusters,represented by the two radar systems with overlapping coverage use the same II Code, every cluster will only be aware of A/C which are not acquired and locked out already by the other system.
To give the controllers in both clusters full situational awareness on the air traffic situation or in military terms to build up an Recognised Air Picture it is necessary to exchange at least 24 Bit Adress and position data between the clusters to enable each cluster to get all A/C within coverage under control.
mil. RADNET
civ. RADNET
Firewall
Military Control and
Reporting Center
Air Defense
Track Server
Track to Track Correlation
Asterix Cat 348
Asterix Cat 48

14. Creation of military ASTERIX Formats
Mil. ASTERIX Cat 348
Target Data
EUROCONTROL ASTERIX format
CAT 48 Mode S
mil. Target Data
Position
Strobedata
Jamminginformation
Status Data etc.
(already defined)
milASTERIX consists of ASTERIX Cat 48 and an military appendix with specific military data. It could be named Cat 348.
Military Format
Extension

15. Civil / military Mode S Radar Data Exchange
Folie 3
Civil / military Mode S Radar Data Exchange
civil
En-Route
Radar
local
military
user
military
ASR
military
user
Civil
RADNET
mil
Track
Control
mil
Plot
civ Plot
Gateway
Firewall
Military
Track Server
civil
Track
Server
civ
Track
The functional architecture in Germany for civil/military Radar Data exchange will be as follows:
There will be two independent Radar Data Networks with independent configuration control and Management.
Whithin each network all main data sources e.g. Sensors and track servers will send their data to every sink (control system) which requires the data.
Both RADNET‘s are using the same Radar Data Format, ASTERIX or milASTERIX. The milASTERIX consists of ASTERIX Cat 48 and an military appendix with specific military data. It could be called Cat 348.
If a mil center needs civ Radar Data, the formatted Cat 48 data will be sent via the gatewax to the mil center.
In the other direction Cat 348 is sent to the gateway, the mil appendix is stripped and Cat 48 is sent to the civil control center.
This technic will save time becaus there is no conversion between civ and mil radar data and it will enhance accuracy due to the fact that there is no conversion loss.
civil
ASR
military
RADNET
military
Long Range
Radar
Control
civil
user
local civil
user

16. Mode S only all call Interrogation
Military use of Mode S
Mode S only all call Interrogation
Mode S reply with 24 Bit adress
Mode S interrogation cycle:
- Mode S only All Call
- Mode S reply with 24 Bit adress

17. Mode S selective Interrogation
Military use of Mode S
Mode S selective Interrogation
Mode S reply with FP Callsign
Mode S interrogation cycle:
- Mode S selective interrogation with 24 Bit adress
- Mode S reply with Flight Plan Callsign or other extracted data

18. Military application: Deviation Advisory via Mode S Functions
Selective interrogation consisting of
Deviation advisory message:
„alter course to heading 123°, you are entering danger zone
Mode S interrogation cycle:
- Mode S selective interrogation with 24 Bit adress and additional uplink message

19. ACAS II Functionality, Mode S based
Traffic Advisory Area
Resolution Advisory Command Area
IFF Mode 3/A, C
Transponder
1. Mode Aonly, Mode C only interrogation
2. Mode A Mode C Reply
Range, Bearing
SSR Mode 3/A, C
Transponder
1. Mode C only “All Call” Interrogation
E-TCAS
2. Mode C Reply
Range, Bearing, Altitude
ACAS
Animated self explanatory slide.
1. Mode S
Transponder
squitters with
24 Bit Adress
2. Mode S Interrogation with received 24 BitAdress
Range, Bearing, calculates closure rates
3. Mode S Reply
with 24 Bit Adress

20. ACAS Traffic Advisory in a civil environment
When reaching a selectivly adoptable range, the fighter will cause a Traffic Advisory in the ACAS equipped A/C.

21. ACAS Resolution Advisory in a civil environment
Without Intercept Bit
Descend
Descend Now !
When reaching a selectivly adoptable range, the fighter will cause a Resolution Advisory in the ACAS equipped A/C.

22. ACAS IC Bit escort announcement in a civil/military environment
With Intercept Bit set
Military Escort Mission
When reaching a selectivly adoptable range, the fighter with activated Intercept Bit will cause a military Announcement instead of a Resolution Advisory in the ACAS equipped A/C.

23. Automated Dependent Surveillance Broadcast System (ADS-B)
Communication
Sattelite
Global
Navigation
Sattelite
ADS-B Receiving Station
NavSys generates
Position Reports
GNSS based
via Mode S Broadcast
With Automated Dependent Surveillance, every A/C broadcasts its Nav System derived Position and other flight data in regular intervals.
The data will be received and fed to Gnd based ATC systems to enhance the tracking performance of the ATM system.
As data link there are VHF, Mode S downlink Extended Squitter and Universal Access Transponder techniques available.
The future may be a Satcom System to be independend from ground based infrastructure at least in desert or oceanic areas.
The problem is that anyone equipped with hand held receiver and Notebook is able to receive and exploit a/c performance and availability data !
Intercepted
Signals
Give away:
ATC System
Performance
Availability
TTP

24. German Order of Electronic Identification
Equipped with hand held receiver and Notebook anyone is able to receive and exploit a/c performance and availability data !
These data are classified !
If mil. uses fixed 24 bit adresses, anyone could rapidly exploit these data for all military aircraft !
To avoid Exploitation the 24 Bit adresses must be masked (e.g. changed for each mission)
Explanation for the operational requirement to mask the 24 Bit adress of military A/C.

25. Mode S Extended Squitter Position Reporting (ADS-B)
LH 123
No ID without Mode S
BA 5643
GAF 2213
With the Mode S Extended Squitter, which was developed for ADS-B ID, position- and other data are broadcasted and will be received from properly equipped systems without active interrogation (under emcon conditions).
This enhances SA (Situational Awareness) of civil airtraffic under line of sight conditions without external support.
Platforms without Mode S are not visible to passive Mode S systems.
Without active Interrogation:
- Flight Plan Callsign
- Longitude
- Latitude
- Height

26. Interoperability of Mk XII A/S in Mixed Environments
ADS-B Mode S Position Reporting
Mil IFF Position
Reporting
In a Mixed Environment as it is possible during peace keeping missions military systems are capable by receiving civil and military position reports to keep situational awareness without active interrogation.
If necessary the systems may interrogate actively using Mode S and military IFF Formats.
Tracker - IDCP
FO/FAC
ADS B, Mode S
Mode S MSSR
Mil IFF Ground
Mil IFF Ground
Mil IFF Report
Tactical Data Link
Mil IFF Air/Sea

27. Intended use of military ACAS
ACAS Communication
ACAS Position keeping
The first intention for the military community to use ACAS was position keeping in formation flying.
As this has negative effects on the environment by increased RF load in the vicinity of a formation other technical solutions were checked for this purpose.

28. Military Hybrid Surveillance with ADS-B
ACAS Communication
Mode S Position reporting in
Formations (Hybrid Surveillance)
An other approach of using Mode S to enhance saftety and to reduce RF pollution was found by using hybrid surveillance for position keeping in formations instead of using active ACAS interrogations.
Every military A/C will be fitted with a Mode S transponder and extended Squitter capability. Those with ACAS or active interrogation capability (Fighter A/C) could additionally receive the extended Squitter and use it for formation flying and for SA.
Position reporting with Mode S provides Situational Awareness
(requires Mode S downlink receive mode)

29. Traffic Information System – Broadcast (TIS-B)
The combined Air and Ground Picture will be
broadcasted to ground traffic on the airport and to
airtraffic in the vicinity of the Terminal Area to
inform on the traffic situation.
Service Volume
TIS-B Traffic Information Volume
Self explanatory slide.
Source: EUROCONTROL 2002

30. Military use of Traffic Information System – Broadcast (TIS-B)
Instead of the combined Air and Ground Picture,
the area of a Danger- or Restricted Zone could
be broadcasted to all airtraffic in the vicinity
TIS-B Traffic Information Volume
Danger or restricted zone
Self explanatory slide.

31. Enhance civil/military Interoperability and flight safety
Summary
Military aspects on Mode S are different from civil ones but military use of Mode S and Mode S related functions will:
Enhance civil/military Interoperability and flight safety
reduce misinterpretation of reactions in conflict areas and
increase Situational Awareness in low level conflict areas
Recommendation:
Support civil/military working groups at national and international organisations as EUROCONTROL, NATO and ICAO to improve civil / military coordination.
Reasons behind:
The military community in most cases recognise changes in equipment, technics and applications when they are made mandatory by national authorities or are recommended by international bodies.
As planning and procurement cycles for military equipmen are quite long, in most cases it is to late to react properly and in time.
Improved coordination would increase understanding and at least interoperability.

33. END.